1. Field of the Invention
The present invention generally relates to a color liquid crystal display device. More specifically, the present invention is directed to a matrix type color liquid crystal display device capable of displaying a full-color image on a color liquid crystal device television.
2. Description of the Related Art
In the conventional color liquid crystal devices, two typical electrode patterns, as illustrated in FIGS. 1 and 2, have been proposed. These color liquid crystal devices are suitable for displaying a full-color image such as a television screen or the like.
The color liquid crystal display device shown in FIG. 1 is known as a so-called "stripe electrode type LCD (liquid crystal device)". This stripe electrode type color liquid crystal display device is constructed of; a large quantity of horizontal stripe-shaped common electrodes (also referred to as "scanning electrodes") C1, C2, C3, . . . , formed on one of a pair of transparent substrates which are positioned opposite to each other with sandwiching a liquid crystal layer (not shown in detail); and a large quantity of vertical stripe-shaped segment electrodes (also referred to as "signal electrodes") R1, R2, R3, . . . , formed on the other of the abovementioned pair of transparent substrates. These vertical stripe-shaped segment electrodes R1, G2, B3, . . . , are crossed with the horizontal stripe-shaped common electrodes C1, C2, C3, . . . . The first and fourth segment electrodes R1, R4 are allocated, for instance, to a segment electrode for displaying a red pixel, and red filters are formed on these segment electrodes R1 and R4. The second and fifth segment electrodes G2, G5 are allocated, for example, to a segment electrode for displaying a green pixel, and green filters are formed on these segment electrodes. The third and sixth segment electrodes are allocated, for instance, to a segment electrode for displaying a blue pixel, and blue filters are formed on these segment electrodes. It should be noted that the remaining segment electrodes (not shown in detail) are allocated to predetermined color-filtered segment electrodes. In FIG. 1, symbols X1, X2, . . . , represent terminals of the respective common electrodes C1, C2, . . . , whereas symbols Y1, Y2, Y3, . . . , indicate terminals of the corresponding segment electrodes R1, G2, B3, . . . .
Display operation of these stripe electrode type color liquid crystal display device is performed by sequentially driving these common electrodes C1, C2, . . . , and by selectively driving each of these segment electrodes R1, R2, R3, . . . , in synchronism with the driving operation of these common electrodes. The fullcolor display by the stripe electrode type color liquid crystal display device can be realized by combining three different pixels. That is, the red pixels which are displayed or illuminated on the intersecting portions between the red-filtered segment electrodes R1, R4, . . . , and common electrodes C1, C2, . . . , are combined with the green pixels which are displayed on the intersecting portions between the green-filtered segment electrodes G2, G5, . . . , and common electrodes C1, C2, . . . , and also the blue pixels which are displayed on the intersecting portions between the blue-filtered segment electrodes B3, B6, . . . , and the common electrodes C1, C2, . . . , respectively.
The color liquid crystal display device shown in FIG. 2 is so-called as a dot electrode type color liquid crystal display device. The dot electrode type color liquid crystal display device is arranged by: segment electrodes for displaying red pixels R1, R4, . . . ; segment electrodes for displaying green pixels G2, G5, . . . ; and segment electrodes for displaying blue pixels B3, B6, . . . , and similarly a number of common electrodes C1, C2, . . . . As is shown in FIG. 2, the respective segment electrodes are positioned in such a manner that a width of each of these segment electrodes in the vertical direction (viewed in the drawing) is selected to be an approximately 1/2 (a half of) width of each of these common electrodes C1, C2, . . . . In other words, these segment electrodes R1, G1, B1, . . . are positioned like a dot-shaped pattern. Also, these dot-shaped segment electrodes are aligned in upper and lower lines along the longitudinal direction of the respective common electrodes C1, C2, C3, . . . , i.e., in the horizontal direction as viewed in FIG. 2, in such a condition that one dot-shaped segment electrode, for instance, "R1" located in the upper line of the common electrode C1 is shifted by an approximately 1/2 pitch with respect to the other dot-shaped segment electrode, for example, "G2" positioned in the lower line thereof. That is, each of the dot-shaped segment electrodes positioned in the upper line of the respective common electrodes is alternately positioned with keeping a 1/2 positional shift with respect to each of the corresponding dot-shaped segment electrodes located in the corresponding lower line thereof. Moreover, the segment electrodes for displaying the same color pixel, e.g., "R1" positioned along the vertical direction, i.e., columns of the common electrodes C1, C2, C3, . . . , are commonly connected with each other via the segment electrodes for displaying the different color pixel, e.g.,"G2" by a signal line "a" and thus a segment electrode terminal Y1, Y2, or Y3. As a result, the color liquid crystal display device is formed as the dot-shaped electrodes for each segment electrode R1, G2, or B3 to display the desired color pixels in such a way that an approximately half portion of the respective dot-shaped segment electrodes is overlapped over another half portion of the corresponding dot-shaped segment electrodes along the vertical direction. This color liquid crystal display device is operated by sequentially driving the combined three different color pixels which are positioned in a triangle relationship, that is similar to the pixel driving operation, so as to display the full-color picture.
The stripe electrode type color liquid crystal display device shown in FIG. 1 has the following drawback. That is, since the stripe-shaped segment electrodes for displaying the color pixels R1, R4, . . . ; G2, G5, . . . ; and B3, B6 are alternately arranged as illustrated in FIG. 1, the same color pixels are aligned in the vertical direction although the three different color pixels, i.e., red, green and blue are alternately arranged or displayed. As a consequence, the color balance of this stripe electrode type color liquid crystal display device is deteriorated, but also red, green, and blue color strip patterns appear in the displayed image. Moreover, since the width of the respective color pixels are substantially equal to those of the respective common electrodes, namely, a pixel having a great area in the vertical direction, the individual color pixels appear considerably so that the image quality of the stripe electrode type color liquid crystal display device is lowered.
The dot electrode type color liquid crystal display device, on the other hand, overcomes, to some extent, the above-described color balance belonging to the stripe electrode type color liquid crystal display. This is because the respective color pixels of the segment electrodes R1, R4, . . . ; G2, G5, . . . ; B3, B6, . . . are alingned in both upper and lower lines of the corresponding common electrodes C1, C2, . . . under the condition that each of the segment electrodes located in the upper line is shifted by a 1/2 pitch with respect to the corresponding segment electrodes positioned in the lower line. Similarly, this dot electrode type color liquid crystal display device shown in FIG. 2 overcomes the stripe pattern appearance of the same color pixels, viewed in the vertical direction, as compared with that of the stripe electrode type color liquid crystal display device, because the same color pixels aligned in the vertical direction are spaced with each other at an approximately 1/2 interval of the full width of the common electrode in the vertical direction. Although the width of the respective segment electrodes R1, G2, B3, . . . , in the vertical direction is narrower than that of the common electrode, i.e., an approximately half of the full width of the common electrode, another width of the segment electrodes in the horizontal direction is approximately two times greater than the width thereof in the vertical direction (in case that the screen size and the column number of the segment electrodes are the same). As a result, the following similar appearance problem of the displayed color pixels is provided as in the stripe electrode type color liquid crystal display device. That is, the respective color pixels of the dot electrode type color liquid crystal display device can be recognized as such color pixels of the stripe electrode type color liquid crystal display device, which are inclined at a right angle with having the same size.
If the column number of the segment electrodes is furthermore increased and the widths of the respective segment electrodes R1, G2, B3, . . . are made narrow of the above-described conventional dot electrode type color liquid crystal display device, then the image quality may be increased while each of the color pixels does not particularly appear. However, if so, then other different problems may be provided. That is, since the respective columns of the segment electrodes R1, G2, B3 . . . , are separately driven in the conventional dot electrode type color liquid crystal display device, the large-scaled segment driver circuit is necessarily required when the column number of the segment electrodes is increased so as to make the horizontal widths of the respective segment electrodes R1, G2, B3, . . . , narrow. In addition, the sampling frequency of the picture signal must be selected to be higher than that of the normal-scaled dot electrode type color liquid crystal display device. This implies that to set the higher sampling frequency, the expensive, high performance circuit elements are required to construct the entire circuit, and the higher power consumption is needed.